GEEEN ALG^. 37 



In some species the sexual organs are borne directly on the filament 

 (Fig. 21, 0). 



Large zoospores are formed in some of the green felts (Fig. 22, A), and 

 are produced singly in the ends of branches that become swollen, dark 

 green, and filled with very dense protoplasm. This end becomes separated 

 by a wall from the rest of the branch, the end opens, and the contents 

 escape as a very large zoospore, covered with numerous short cilia (A n). 

 After a short period of activity, this loses its cilia, develops a wall, and 

 begins to grow (in, iv). Other species (B) produce similar spores, which, 

 however, are not motile, and remain within the mother cell until they are 

 set free by the decay of its wall. 



ORDER V. Characece. 



The Characece, or stone-worts, as some of them are called, are 

 so very different from the other green algae that it is highly 

 probable that they should be separated from them. 



The type of the order is the genus Chara (Fig. 23), called 

 stone-worts from the coating of carbonate of lime found in 

 most of them, giving them a harsh, stony texture. Several 

 species are common growing upon the bottom of ponds and 

 slow streams, and range in size from a few centimetres to a 

 metre or more in height. 



The plant (Fig. 23, A) consists of a . central jointed axis 

 with circles of leaves at each joint or node. The distance 

 between the nodes (internodes) may in the larger species 

 reach a length of several centimetres. The leaves are slen- 

 der, cylindrical structures, and like the stem divided into nodes 

 and internodes, and have at the nodes delicate leaflets. 



At each joint of the leaf, in fruiting specimens, attached to 

 the inner side, are borne two small, roundish bodies, in the 

 commoner species of a reddish color (Fig. 23, A, r). The 

 lower of the two is globular, and bright scarlet in color ; the 

 other, more oval and duller. 



Examined with a lens the main axis presents a striated 

 appearance. The whole plant is harsh to the touch and brittle, 



